What to do about my cat peeing outside the box?

I have had two cats for over a decade now--one male and one female. my family got them when I was a little girl, and they're growing older (still just as cute though!). However, for almost as long as we've had these two, the boy cat has been a trouble maker. A few years ago, he started peeing outside of the... show more I have had two cats for over a decade now--one male and one female. my family got them when I was a little girl, and they're growing older (still just as cute though!). However, for almost as long as we've had these two, the boy cat has been a trouble maker. A few years ago, he started peeing outside of the box, and on couches, bags, walls, and anything else he can find. we tried everything to combat it--more litter boxes, new types of litter, boxes in new locations. he's also been neutered since he was kitten. My mom works so hard to take care of these cats--she always cleans up his accidents and I help her as much as I can, but I always feel like it's not enough. We've even taken him to the vet several times about the issue and he has no serious health issues (except being overweight, which he always has been, and a tooth infection that got fixed). This bad behavior has become a habit for him and causes so much stress on my family, and I worry that it causes stress on the kitties too! Does anyone have any advice? Has anyone been through something similar? I will do whatever it takes to help my cats, and to help my mom out. I hate how much stress she's under with these pets, who we all love dearly and would never get rid of. Thank you for any help you could give.
Update: Edit: I believe he's spraying, not peeing. He backs up against the object and shakes/vibrates his tail, and sprays the surface. It's so strange because he was neutered/fixed as a baby! And he and his sister have been together their whole lives. they do fight sometimes but generally get along, and always have.
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